I think it depends on each agencies policy. A friend who works for a local PD can carry his choice after he qualifies with it. As far as I know, he has to use issued ammunition when he carries off duty.

That's true Mr. G., every agency is different. It was only about ten years ago that we were allowed to carry semi automatics off duty (not including our duty weapon). We could only carry .38/.357 snubbies prior.